1993 4.3 w 4x4
usually runs great well as good as it can for 175K i had egr build up problems before and had to clean the egr and would run fine haven't had much problem but lately i will come to a stop and the idle seems to drop and almost die then i take off and everything is fine. i can never seem to get the problem to happen twice. so its hard to diagnose has any one had this happen their is no gas smell from plenum or build up on egr or leaks in brake booster. could my fuel pump be trying to die on me causing fuel pressure differentials.

 

i have a 94 and having almost the same issue it seems to almost die when im at a stop i looked for vac leaks found 2 but but its still running the same i ordered the iac idle air control to see if its the problen cuz one day this happened it ran fine the next then back to crap i unplugged it to see if it made a diff and still ran the same . ima look at the egr n see how it looks and letr u know if the iac was my prob

 

I also have a 94 vortec 4.3 and have a similar problem. I just replaced the spider injector, FPR, Nut Kit, gaskets to upper and lower manifold, fuel filter, new cap, rotor, and plugs. Brought the beast back to life, at least she starts now, but while at a stop or in park, the idle will go down low.. then back up, or it will stall out.

My brother thinks this is a timing issue. I know the beast needs some new wires, but would that be the cause of this new problem? I was thinking AIC but have no money for anymore parts right now. Could this be an issue with the cam position sensor or distributor? I originally marked the dist. wrong and had to find where TDC {top dead center} was to get the truck to run, perhaps i am off by one tooth. Any thoughts?

 

i seem to be having the same problem with my '91 4.3 v6. when im running it is smooth. but when i come to a stop, the idle seems to drop a bit and it feels like it wants to stall on me. if anyone has an idea of what it can be let us know.

 

ok first i changed the fpr then when it started acting up again i thought it was a vac line so i looked all over n couldn't find 1 then i replaced the aic thinking it was it but same issue with it wanting to cut out so i took the egr off and found a big chunk of deposit in there ale the spring loaded area was stuck in so i cleaned it up a bit to loosen it now its running good i might change it out later hope this helps

 

Decided to take out the dist again and move it to another tooth... after a few tries i got it to run, but now the problems are different. Now she'll idle kinda rough, but completely lacks power! I could at least drive down the street before i did that.

I may just be making it worse everytime i take out the dist. and should just do the TDC thing again, but is that very accurate? {Im referring to taking out #1 sparkplug and making sure piston is out all the way and making rotor point to #1 wire on the cap.}
and do you think that is the problem, or did something else get destroyed like the connector to the injector when all that gas got into the plenum?
or possible cam position or crank position sensor? Couldve screwed those up while messing with dist. {is that where they are?}

I bought some new plugwires today, so im gonna go throw those on and see if anything changes. The old ones on there are really not reliable and dont get good connection.
Cleaned out the EGR the other day, not much in there... still could be AIC too, but still too poor to just throw parts at it. Next task, i need to test the fuel pressure and make sure it isnt the fuel pump {read about those symptoms on another thread and they are kinda similar} I know i have some broken vacuum lines behind the dist cap, but im not even sure what plugs into where so fixing those is gonna be another project. I wouldnt think those small vacuum lines would be causing these major problems, but ive been known to be terribly wrong about almost everything , so..... :P

Ahh... always dealing with a full plate on an empty stomach. I'll let you know how it works out.

 

All of you guys should get your truck going with the hood open, and pull and jiggle on that blue/red wires that come out the drivers front of the plenum... What happens now? Nothing should change. If you get a stall or poor run condition then you will want to change out your injector harness. They are about 15 bucks at NAPA, and if they cant seem to find the part number for you, then ask for an injector connector for a 95 half ton truck, they are the same part. Cut, solder, and re-connect, done.

The problem is that little insert in the connector thats made out of some ****ty rubber compound. Rubber doesnt not like being in a petroleum rich environment and deteriorates over time, making the plug loose on the injector top. The new one has a silicone thing instead of rubber, and holds that connector on nice and tight.

I had the same things going on with my blazer. It runs smooth with any RPM, but at idle shakes and wants to stall out. The shaking was making this connector wobble and make a poor connection.

 

All of you guys should clean out your iac valves!!!

 

As for the TDC thing, thats exactly how you make sure you have the ignition timing spot on! However, you need to make sure that piston is on its compression stroke and not an exhaust stroke. If its on an exhaust stroke your timing is 180 degrees out. In that case, spin your distributor 180 and try again. I just stick a 90degree pick down the spark plug hole and feel that both valves are closed (you wont be able to feel a valve if they are both shut, if you feel the one open that lines up with the exhause manifold then you know you are on an exhaust stroke) to know that the piston is on the right cycle, then drop the distirbutor in pointed to plug 1.

The connector to the injector most certainly gets destroyed by your old fuel leak, its a 15 dollar part, you should change it if there is any play at all in it.

Darn tooting you can get a poor run condition with those little vaccum lines leaking, thats what you get a lean run condition from, which is no good in the long run. Not to mention your heater controls, or 4wd or timing advance wont work properly. Grab 10 feet of bulk vaccum line and replace them all. The vaccum system is not that hard to figure out at all. The hoses get hard and brittle and usually are not that far from where they should be connected since they lose flexibility from the heat. If you really dont know where it goes, then plug it with a bolt until you figure out where it should go - that way you stop the vaccum leak.

I will take some photos of my vaccum lines tomorrow evening when the wife gets back with the truck and maybe make a sticky with decent photos that Kyle can put in the help section... Something for me to work on, and to give a little back to the forum thats been alot of help for me in the past.

 

The details of how the vacuum lines hook up would me most helpful, thanks!

I finally got my beast running better! It was a simple turn of the distributor casing {not the toothed core} i was in the right tooth, just didnt know it mattered so much how the whole dist sits... Something to consider if you've recently had to take it out and the truck isnt running good or has a strange idle after re-installation. This was an easy fix for me, seeing as i could get a small socket wrench back there to loosen the hold down clamp without disturbing or dismantling everything over and over again. Then turned the dist with cap attached counter-clockwise as far as it would go and bam! Got all my power back and the idle is {closer to} normal. Happy happy, joy joy!

Im going to replace the injector connector as well, seeing as everyone who went through this job has needed to replace it. There is also a bit of play in my connector, so i'll call it 'preventive car repair' and fix it before it becomes a major pain in the ***

Although i havent taken it on the highway yet, i drove it down the street and let it get up to operating temp before driving it home and shutting it off. Re-started just fine a few hrs later. Gotta take it for a longer drive now.. good luck, my friends... and thanks so much for all the valuable info listed on this site. Couldnt have done it without your expertise!